Influence of crystallization conditions on the structure and thermal behavior of syndiotactic polystyrene

The dependence of the crystal structure and morphology of syndiotactic PS on crystallization conditions was studied by the XRD, DSC and atomic-force microscopy techniques. It was found that the final structure in the case of melt crystallization was determined by the melt overheating temperature. Below 280°C, the melt contains triplets, which form the limit ordered α" form upon subsequent crystallization. The crystallization rate is high and the size of crystallites does not vary with time under these conditions. Overheating to 320°C leads to the complete degradation of triplets, and the thermodynamically more stable β modification is formed in substantially slowed crystallization. Low nucleation and growth rates allow crystallites with lateral dimensions up to 850 Å to be obtained. The limiting disordered crystalline a' form is produced by annealing the quenched melt with the triplet structure; as the annealing temperature increases, the degree of crystallinity and the lateral size of crystallites monotonically increase. The kinetics of crystallization determines the super-molecular structure of the samples. It was shown that samples containing the α form are characterized by the sheaflike morphology and the absence of a long spacing. Crystallization in the β form leads to spherulitic morphology and to the appearance of the long spacing.SCOPUS: ar.jinfo:eu-repo/semantics/publishe